Understood. I am sure you tried this already, but I would make sure you have all the latest drivers and updates for the hardware and software. Try giving it a fresh install... meaning uninstall Cubase LE and the hardware and start new. I realize this takes time, but it will allow us to start from scratch.
Something like this is difficult to trouble shoot via a forum, so I can only suggest the steps I would take. I find that a fresh install often fixes most problems. If this doesn't help, give me a private email and we can go from there.
Thanks.